Constant velocity joints connecting interconnecting shafts to drive units are common components in automotive vehicles. The drive unit typically has an output shaft or an input shaft for receiving the joint. Typically, the drive unit is an axle box, transfer case, transmission, power take-off unit or other torque device, all of which are common components in automotive vehicles. Typically, one or two joints are assembled to the shaft to form a propeller or drive shaft assembly. It is the propeller shaft assembly that is connected, for instance, at one end to the output shaft of a transmission and, at the other end, to the input shaft of a differential. The shaft is solid or tubular with ends adapted to attach the shaft to an inner race of the joint thereby allowing the outer race connection to a drive unit. The inner race of the joint is typically press fit, splined, or pinned to the shaft making the outer race of the joint available to be bolted or press fit to a hub connector, flange or stubshaft of the particular drive unit. At the other end of the propeller shaft, the same typical connection is made to a second drive unit when connecting the shaft between the two drive units.
Motor vehicles commonly use propeller or drive shafts to transfer torque from the one input unit to an output unit, e.g. from a front drive unit to a rear axle differential such as in rear wheel and all wheel drive vehicles. Propeller shafts are also used to transfer torque and rotational movement to the front axle differential in four-wheel drive vehicles. In particular, two-piece propeller shafts connected by an intermediate joint are commonly used when larger distances exist between the front drive unit and the rear axle of the vehicle. Similarly, inboard and outboard axle drives are commonly used in motor vehicles to transfer torque from a differential to the wheels. The torque transfer is achieved by using a propeller shaft assembly consisting of one or two joints assembled to an interconnecting shaft in the manner indicated above.
Joint types used include Cardan, Hooke or Rzeppa type universal joints. Typically, Rzeppa type constant velocity joints are employed where transmission of a constant velocity rotary or homokinetic motion is desired or required. Constant velocity joints include tripod joint, double offset joint, and cross groove designs having plunging or fixed motion capabilities. The tripod type constant velocity joint uses rollers or trunions as torque transmitting members and the other constant velocity joint types use balls as torque transmitting members. These types of joints assembled to an interconnecting shaft are applied in inboard axle and outboard axle drives for front wheel drive vehicles, or rear wheel drive vehicles, and on the propeller shafts found in rear wheel drive, all wheel drive, and four-wheel drive vehicles allowing for angular articulation or axial motion.
The torque transfer capability of a drive shaft is primarily influenced by its moment of inertia, which is primarily a function of the maximum radius of the shaft rather than its mass. Thus, it would be desirable to have a shaft to joint connection that benefits from the torque transfer to radius relationship to reduce the mass of the assembly. Moreover, it would also be desirable to provide a system that eliminates unnecessary components, such as the stubshafts or the flanges, thereby providing a drive system connection that has less weight for a given torque transfer capability. Moreover, a connection system that provides a reduced package size for a particular constant velocity joint assembly would also be of benefit. Also, a connection system with optimized ratios would provide additional benefits, such as weight reduction, package size control, reduced number of parts and/or part runout, improved vibration deadening, increased bending stiffness, increased torsional stiffness, and reduced assembly time of propshaft to vehicle connection.
It would be advantageous to have the above-mentioned improvements by providing optimized ratios in attachment methods, particularly in attachment methods for propeller shaft connections utilizing constant velocity joints. While automotive manufactures and suppliers commonly refer to constant velocity joint as, for example, without limitation, DL, VL, GI, AAR, SC and XL type joints, the invention, below, relates to these types of joint configured by optimized ratios in attachment methods to obtain a Direct Torque Flow (DTF) connection.